In recent years, thermal transfer systems have been developed to obtain prints from pictures which have been generated electronically from a color video camera or digital input. According to one way of obtaining such prints, an electronic picture is first subjected to color separation by color filters. The respective color-separated images are then converted into electrical signals. These signals are then operated on to produce cyan, magenta and yellow electrical signals. These signals are then transmitted to a thermal printer. To obtain the print, a cyan, magenta or yellow dye-donor element is placed face-to-face with a dye-receiving element. The two are then inserted between a thermal printing head and a platen roller. A line-type thermal printing head is used to apply heat from the back of the dye-donor sheet. The thermal printing head has many heating elements and is heated up sequentially in response to the cyan, magenta and yellow signals. The process is then repeated for the other two colors. A color hard copy is thus obtained which corresponds to the original picture viewed on a screen. Further details of this process and an apparatus for carrying it out are contained in U.S. Pat. No. 4,621,271, the disclosure of which is hereby incorporated by reference.
Dye-receiving elements used in thermal dye transfer generally comprise a polymeric dye image-receiving layer coated on a base or support. Transport through the thermal printer is very dependent on the base properties. For acceptable performance, the dye-receiving element must have low curl under a wide variety of environmental conditions, conditions at which the printer will be operating. From an aesthetics standpoint, it is also desirable for the dye-receiving element to exhibit low curl under the wide variety of environmental conditions at which the print will be displayed or kept.